xsiborg, very nice tank!
Are your dendro polyps shearing right off and do you have bright yellow fluffly things all over the stalk? If so, try to get your hands on a good anthelmintic (de-wormer). If you can find a source for Levamisole, get it. Assuming it is not already too late, I think it should work. Doing coral dips in saltwater with the anthelmintic would be the way to go. I tried flatworm exit, and it seemed to kill a good number of them. But, I think it was too late. I bought a different anthemintic, Praziquantel, in case I have this problem in the future.
Also, don't discard the skeleton after the dendro dies! I have like 10 new baby polyps that grew on it.